In oil and gas exploration it is desirable to understand the structure and properties of the geological formation surrounding a borehole in order to determine if the formation contains hydrocarbon resources (oil and/or gas), to estimate the amount and producibility of hydrocarbon contained in the formation, and to evaluate the best options for completing the well in production. A significant aid in this evaluation is the use of wireline logging and/or logging-while-drilling (LWD) or measurement-while-drilling (MWD) measurements of the formation surrounding the borehole (referred to collectively as “logs” or “log measurements”). Typically, one or more logging tools are lowered into the borehole and the tool readings or measurement logs are recorded as the tools traverse the borehole. These measurement logs are used to estimate the desired formation properties.
One popular way to obtain the measurement logs is NMR logging. NMR logging has become very important for purposes of formation evaluation and is one of the preferred methods for determining formation parameters because of its non-destructive character. Improvements in the NMR logging tools, as well as advances in data analysis and interpretation allow log analysts to generate detailed reservoir description reports, including clay-bound and capillary-bound related porosity, estimates of the amounts of bound and free fluids, fluid types (i.e., oil, gas and water), permeability and other properties of interest. In general, NMR logging devices may be separate from the drilling apparatus (in what is known as wireline logging), or they may be lowered into the borehole along with the drilling apparatus, enabling NMR measurement while drilling is taking place. The latter types of tools are known in the art as logging-while-drilling (LWD) or measurement-while-drilling (MWD) logging tools.
NMR tools used in practical applications include, for example, the centralized MRIL® tools made by NUMAR Corporation, a Halliburton company, and the sidewall CMR tool made by Schlumberger. The MRIL® tool is described, for example, in U.S. Pat. No. 4,710,713 and in various other publications including: “Spin Echo Magnetic Resonance Logging: Porosity and Free Fluid Index Determination,” by Miller, Paltiel, Gillen, Granot and Bouton, SPE 20561, 65th Annual Technical Conference of the SPE, New Orleans, La., Sep. 23–26, 1990; “Improved Log Quality With a Dual-Frequency Pulsed NMR Tool,” by Chandler, Drack, Miller and Prammer, SPE 28365, 69th Annual Technical Conference of the SPE, New Orleans, La., Sep. 25–28, 1994. Certain details of the structure and the use of the MRIL® tool, as well as the interpretation of various measurement parameters are also discussed in U.S. Pat. Nos. 4,717,876; 4,717,877; 4,717,878; 5,212,447; 5,280,243; 5,309,098; 5,412,320; 5,517,115, 5,557,200; 5,696,448; 5,936,405; 6,005,389; 6,023,164; 6,051,973; 6,107,796; 6,111,408; 6,242,913; 6,255,819; 6,268,726; 6,362,619; 6,512,371; 6,525,534; 6,531,868; 6,541,969; 6,577,125 and 6,583,621, as well as in application Ser. No. 60/474,747, filed on May 3, 2003, to the same assignee as the present application. The structure and operation of the Schlumberger CMR tool is described, for example, in U.S. Pat. Nos. 4,939,648; 5,055,787 and 5,055,788 and further in “Novel NMR Apparatus for Investigating an External Sample,” by Kleinberg, Sezginer and Griffin, J. Magn. Reson. 97, 466–485, 1992; and “An Improved NMR Tool Design for Faster Logging,” D. McKeon et al., SPWLA 40th Annual Logging Symposium, May-June 1999. The contents of the above patents and patent applications are hereby expressly incorporated by reference for all purposes, and all non-patent references are incorporated by reference for background.
An application of NMR and other logging techniques is using measurement data to analyze the anisotropy of certain properties of the geological formation. Such properties may include permeability, porosity, resistivity, diffusivity, or viscosity. Anisotropic analysis of properties is particularly useful in reservoir engineering in which data or logs obtained through multiple measurements at different locations need to be combined, so that each flow interval of the geological area is characterized by a single anisotropy, such as permeability anisotropy. The process of combining data is often referred to as “up-scaling”. Up-scaling can be very difficult because the measurement data are often taken at various scales and using different sample sizes. Moreover, without a well-defined algorithm to combine the data, an upscaled log is difficult to create for a path comprising a plurality of possibly different spatial units.
One purpose of upscaling is to use the single anisotropy, such as permeability anisotropy obtained for a flow interval, to predict the producibility of a well. Such performance prediction is traditionally made following well testing. However, the petrophysical industry is becoming more and more reluctant to perform well testing due to the increasing economical and environmental costs. Research is under way to determine whether alternatives, such as wireline formation tests, can be used to replace well test. (See, e.g., “A Comparison of Wireline and Drillstem Test Fluid Samples from a Deep Water Gas-Condensate Exploration Well”, by Witt et al., paper 56714 presented at the 1999 SPE Annual Technical Conference and Exhibition, Houston, Tex., Oct. 3–6, 1999, the content of which are hereby expressly incorporated by reference for additional background.) Developing methods and systems for efficiently creating upscaled logs based on measurement data obtained along a path (or paths) in wireline formation tests can therefore stimulate the transition from well testing to wireline formation tests.
There is therefore a need to develop upscaling method(s), preferably capable of combining different types of data, including core data, wireline logs, wireline tester data and well testing. There is also a need to develop a system to implement the up-scaling method(s).